Automatic telephone system.



J. W 'LATTIG & C. L. GOODRUIVI.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED APR- 25 I916- Patented Nov. 13, 1917.

C/fdf/QS L. Goodr 1. w. LATTIG &'C L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.-

APPLICATION FILED APR- 25, I916.

1,246,619. Patented Nov. 13, 1917.

I 2 SHEETS-SHEET 2- //7l/6/7/0/1S.' Jacofi Vl/ Za/f/y. C/iflf/QS LGood/am. y y W 1 X12 Affy UNITED STATES PATENT oFFioE. f

JACOB W. LATTIG, OF GLENSIDE, PENNSYLVANIA, AND CHARLES L. GOODRUM, OFYORK, N. Y., ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEWYORK, N. Y., A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE SYSTEM.

Application filed April 25, 1916. Serial No. 93,386.

To all whom it may concern.

Be it known that we, JACOB IV. LATTIG and THARLES L. GooDRUM, citizensof the United States, residing at Glens'ide, in the county of Montgomeryand State of Pennsylvania, and at New York, in the county of New Yorkand State of New York, respectively, have invented certain new anduseful Improvements in Automatic Telephone Systems, of which thefollowing is a full, clear, concise, and exact description. I

This invention relates to telephone exchange systems employing machineswitching. In systems of this character, 1t frequently happens thatafter a connection has been partially built up, a group of trunks isencountered, all of which are busy. Heretoforc, in such event, thecalling subscriber received a busy signal and had to replace hisreceiver, whereupon the set switches were all automatically restored,and had to be subsequently reset.

A feature of this invention is the provision of a circuit arrangementwherein when in the process of setting up a connection, one of theautomatic switches finds the entire group of trunks busy, a busy signalis transmitted back to the calling party. to inform him of this fact,and when one of the trunks in the group becomes idle, the switch will beautomatically set in motion to seize such idle trunk and to disconnectthe busy tone from the calling line.

Another feature of the invention relates to machine switching telephoneexchange systems employing private branch exchange working, and providesa circuit arrangement for a. system of this character, wherein it ispossible to increase or to diminish the num. ber of private branchexchange trunks allotted to a given number or to change from anindividual subscribers line to a private branch exchange withoutdisturbing the numbers of the subscribers lines connected to theconnector bank contacts.

The invention is illustrated in the accompanying drawings in whichFigure 1 shows in diagrammatic form a connection from a callingsubscriber to a connector switch, the circuits of the latter being shownin detail.

Fig. 2 shows the circuits and apparatus for connecting the privatebranch exchange trunks to the connector switchshown in Fig. 1. e In theembodiment of the invention as shown in thefigures, the invention isillustrated' with a two-wire system, but it will be evident that it maybe readily applied to any oneof the-well-lmown types of automaticsystems. In the system as disclosed, a call to a private branch exchangesystem is switched through the various switches to' a connector switchin the regular manner.- When the call has been extended to the connectorswitch a switching device associated with an idle private branchexchange trunk is operated and connects the calling line with thedesired private branch exchange system.

The invention can be best described by tracing a call from the callingsubstation illustrated in Fig. l to the private branch exchange shown inFig. 2, and a call will be thus traced in the following description.NVhen the calling subscriber removes his receiver from the hook the linefinder shown at 2 will automatically connect his line with an idle firstselector 3. WVhen the subscriber is so connected he will send a seriesof im-- pulses to the first selector diagrammaticallyshown at 8, whichwill connect his line to a trunk leading to a connector switch, in thecontact bank of which are located the terminals associated with thedesired private branch exchange. WVhen the subscriber has been connectedto the connector switch, cur- Specification of Letters Patent.PatentedNoy. 13, 1917.

rent will flow through the line relay 4 which 7 will consequently beenergized. The energization of this line relay closes a circuitfrom-ground by'way of its armature and make contact through theslow-acting relay 5 to battery. The subscriber will now send a series ofimpulses to connect the movable contacts of the connector switch withthe group of terminals containing the line associated with the privatebranch exchange to which connection is desired. When this series ofimpulses is sent, the line relay 4: will vibrate but the slow-actingrelay 5 will remain energized. This will complete a circuit from theground on the armature'of relay 4: by way of its break contact, theright-hand armature and make contact of relay 5 and the coil of theslow-acting relay 6 to battery. The operation of the slow acting relay 6will close a circuit for the side switch magnet 7, which may be tracedfrom the ground on the armature of the relay 8', its break contact, themake contact and armatures of relay 6 and the coil of the side switchmagnet 7 to battery. The circuit completed through theslow acting relay6 contains av parallel branch which may be traced from the make contactof the slowacting relay 5 by way of the sideswitch arm 9 and primarymagnet 10 of the connector switch to battery. The primary magnet 10 willconstantly respond to the vibration of the armature of the line relay 4and this will move the brush-contactsof the connector switch .to a levelwhich will place'it in alinement with the group of contacts whichcontain terminals assigned to a trunk associated with the private branchv exchange system.

' After thefirstset of impulses to the con-- nector switch hasbeen sentby the. subscr1ber,the linev relay st w ll again be energized foradefiniteperiod. This will open the circuit of the slow-acting relay 6 atthe break contact of the line relay 1 and the slow-acting relay 6 willthus be deenergized and in turn will open the circuit of the side switchmagnet 7 previously traced. This will move the side switch arms of theconnector switch into their second position. The subscriber now sends asecond series of impulses which will result in the comple tion ofcircuits similar to those previously traced, for the first set, with theexception that the circuit through the side switch arm 9, which is nowin its second position, will be completed through the secondary magnet12. The secondary magnet 12 will consequently move the brush terminalsto the contacts, in the group selected, assigned to the desired privatebranch exchange system. After the second series of impulses to theconnector switch has been transmitted, the

line relay LWill again be energized for a' of relay 17 to battery. Thiscauses the energization of relay 17 which closes a circuit from theground on its armature by way of its make contact, the normal contacts18 of the first finder switch allotted to the private branch exchangesystem and the break contact, armatureand coil 19 of the motor magnet ofthe finder switch to battery. A parallel circuit is completed fromtheolf-normal contact 18 byway ot the sideswitc'h escape magnet 22 tobattery and the slow-acting relay 23 tobattery, likewise through theright-hand winding of test relay 29 of the finder-switch to battery.Immediately after the finder switch takes its first step, the ofinornial contact spring 18 is moved to its alternate position and theinitial operating circuit of the motor magnet 19, the escape magnet 22,the relay 23 and the test relay 29 is opened; This circuit isimmediately completed, however, by way of the side switch arm25, thebrush 26 and the break contacts and the ground on the armatures ofrelays, similar to relay 17, associated with trunk lines leading toidleterminals assigned to private branch exchange trunks in the variousconnector, switches.

This circuit completed through the armature of relay 17 movesthe'brushes of the finder switch step by step from one group of contactsto the next, until the trunk extending from the connector switch to thefinder switch associated with the calling line is found. l/Vhen thistrunk is located, the circuit for the motor magnet 19, the escape magnet22 and the slow-acting relay 23 is broken at the armature of theoperated relay 17, and consequently the movable terminals of the finderswitch are permanently located on the selected terminal; The escapemagnet 22 in deenergizing moves the side switch arms of the finderswitch into its second position and thereby extends the call from thecallingsubscriber through the contacts of the finder switch to theprivate branch exchange indicated at 27. The circuit of the test relay29 is maintained closed from battery. through its left-hand winding, itsmake contactand' armature, side switch arm 32, brush 33 and itsassociated contact, brush 16 of the connector switch and its associatedcontact and side switch arm 15 to ground. In position 2 side' switch arm80 closesthe circuit of relay 16. Relay 16 in attracting its leftarmature deenergizes relay 17, which, in retracting its armature,grounds the finder multiples 85, thus ren dering the selected trunknon-calling to other finders.

Remembering that the side switch of'the connector is in its thirdposition, it will now be apparent that a signaling circuit to theprivate branch exchange is completed from the generator 54- and thebattery commutator ring 52 through the ringing relay 8, the make contactand armature of side switch magnet 7 which is operated, side switch arm34, brush 35, of the connector switch, and its associated contact, brush36 of the finder switch and its associated contact, out over the privatebranch trunk and back by way of brush 37 of the finder switch, and itsassociated contact, brush 38 of the connector switch and its associatedcontact, side switch arm 40 and the make contact and armature of therelay 4 to ground. The response to this signal from the private branchexchange will increase the flow of current over the circuit just tracedwhich will energize the ringing relay 8 and this will open the circuitof the side switch magnet 7 which in turn will move the side switch armsof the connector switch into their fourth position. In the fourthposition of the side switch'of the connector, the talking strands of thecalling subscriber are connected with the selected private branchexchange trunk. The calling subscriber is now in a position to conversewith the subscriber at the private branch exchange. l/Vhen thesubscribers complete their conversation and hang up theirreceivers,relays 4 and 43 will deener. gize. Relay 4, in retracting its armature,opens the circuit of slow relay 5, which, in retracting its armatures,closes the following circuit for the release magnet 42 of the cornnector free pole of battery, right winding of magnet 42, right armatureand back contact of relay 43, ofi normal contact 44, left armature andback contact of relay 5, left armature and back contact of relay 43,right armature and back contact of relay 5, right armature and backcontact of relay 4 to ground. Release magnet 45 of the selector 3 isalso energized over the following circuit in parallel with magnet 42:free pole of battery, magnet 45, test brush 82, terminal 83, testconductor 84, left armature and back contact of relay 43, rightarmatures and back contacts of relays 5 and 4 to ground. Magnets 42 and45 in operating restore the apparatus of the first selector andconnector switches to normal. The line finder 2 will likewisebe restoredto normal in the usual manner. 7 v

The finder switch shown in Fig. 2 will be restoredby the deenergizationof the test relay 29. It will be remembered that this relay ismaintained in an operated position by means of a locking circuit whichwas traced from battery through its left-hand winding, its make contactand armature, side switch arm 32, brush 33 and its associated contact,brush 16 of the connector switch and side switch arm 15 of the connectorswitch to ground. Consequently, when the connector switch is restored tonormal this circuit is broken at the side switch arm 15 and the testrelay 29.0f the finder. switch is deenergized. The deenergization ofthis re lay causes the completion of a circuit from ground through theoff-normal contact 45, the right-hand armature and break contact of thetest relay 29, and the release relay 46 of the finder sWitch to battery.This will restore the finder switch associated with the selected privatebranch exchange trunk to normal. c

All'the apparatus used in establishing the connection from the callingsubscriber to the private branch exchange system has now been restoredto normal and is in condition to be used for another connection.

By referring to the circuitsh'own in Fig. 2 it will'be observed that buttwotrunks to the private branch exchange system 27 and their associatedfinder switchesjyhave been shown. It will be evident, however,"that anynumber of these trunks, depending upon traffic'conditions,vcan'beallotted to a private branch exchange system, andthat with each one of thesetrunks will be associated a finder switchsimilar to the ones shownin Fig. 2., To simplify the drawing, but two ofthese finders have been shown. 'Allotte'd to the contact bank ofeach-finderswi'tch and wired in multiple are terminals connected to theterminals in thevarious connector switches assigned to the privatebranch exchange system. Each of these contacts in the connector switchare individual to said switch andare not multipled to the otherconnector switches of the group. Associated with each of the trunksleading from the connector switch to the finder switches is a relay 17used to initiate the starting of the first idle finder switch associatedwith the private exchange system 27 and a cut-ofif relay 16, utilized toopen the initial energizing circuit of the relay 117, when the trunk tothe finder switch'asso ciated with the calling line has been found.

But two of the trunk lines from the connector switch to the finderswitch are shown in Fig. 2 and, as shown, these lines are multipledthrough all the finder switches asso ciated with the particular privatebranch exchange system. It will be evident, however,

that the number of terminals in the finder switches associated with theprivate branch exchange systemwill be equal in number to the connectorsin the group to which the private branch'exchange has been assigned. Itwill also be apparent that line switches could be used instead of finderswitches.

It follows from the foregoing description that any set of terminals inthe connector bank may be assigned to a private branch exchange system/Bearing in mind the previous description of the circuits shown in thetwo figures, it becomes apparent that when themovable contacts of anyconnector switch are associated with the terminals assigned to anybranch exchange system, the calling subscriber may be connected bymeans'ofthe finder switches shown in Fig. 2 with any one of a pluralityof trunks tern. Any set of terminals in the ordinary connector bank canbe assigned to a private branch exchange by merely openingthe multipleconnections between the contacts in the switches of the group. As thisset of assigned terminals may then be connected to a plurality of trunksto a private branch exchange system, which may be varied at willdepending upon traffic conditions, 1t follows that the private branchexchange trunking facilities'associated with any connector switch may bechanged without afi ecting in any manner whatsoever the number ing ofcontact terminals in a contact bank of the connector switch. Thus anyone ofa number of contiguous contact terminals in the contact bank ofany connector switch may be changed from a private line to a privatebranch exchange line or v-iceversa, without in any way afiecting thenumbering of all the remaining connected subscriber s lines. Likewise ina connector switch in which all the contacts of the terminal bank arewired to individual lines, it is possible to change any one of saidlines to a private branch exchange line without affecting the numberingof all the remaining connected subscribers lines.

If all the private branch exchange lines allotted to a system are busywhen a calling subscriber attempts to connect with the private branchexchange, the circuits are arranged so that the subscriber will obtain abusy signal indicating this condition and this subscriber may then athis option either hang up his receiver and release the connection, orwait at his telephone, in which case the connected line willbe switchedto the private branch exchange system as soon as one of the trunks tothe system becomes idle.

Referring to the circuit shown in Fig. 1, when the brush contacts 16, 35and 38 are switched to their a-ssociated stationary contacts assigned toa private branch exchange system in which all the trunks are busy, acircuit is completed from ground by way of the side switch arm 15, brush16 and its associated contact and the break contact and armature ofrelay 16 and the coil of relay 17, associated with the trunk leadingfrom the terminals of the connector switch selected to the multiplestationary contacts of the various finder switches associated with theprivate branch exchange trunks, to battery. The circuit just completedwill cause the energization of a relay 1'7 and this will connect theground attached to the armature of said relay, by way of its makecontact, to the extended starter wire connected through the off-normalcontacts 18 and the armatures and break contacts of the slow-acting.relays 23 of the various finder switches. However, as all the finderswitches are engaged, the extended starter wire circuit will-be deadended from the armature. and make contact of the slow-acting relay 23ofthe last finder switch. At the same, time a circuit will be completedfrom ground through the winding 50 ofa transformer, the ofi-normalcontacts 51, 52, etc., of the various finder switches, break contact andarmatureof the relay 16 associated with the trunk selected by 'the,connector switch and thence by way oi brush 85 of the connector switch,side switch 1arm'34, armatureand make contact of the side switch magnet7 the coil of the ringing relay 8 and through the interrupting dislr5land the commutator ring 52, to battery and ground. The completion ofthis circuit will, energize ringing relay 8 which will attract itsarmature and open the energizing circuit of the side switch ,magnet 7,which will move the connector. side switch into its. fourth position.,In this position of the side switch,,a busy tone will be sent back tothe calling subscriber over a circuit which may be traced from groundthrough the winding 50 of, the transformer, the off-normal contacts 51and 52 of the private branch exchange finder switches, the break contactancharmature of relay 16, the brush 35 of the connector switch, sideswitch arm 34k and thence by way of the-ringing strand of the trunksbetween the various switches through the calling subscribers loop andback over the tip strand of the switch trunks, through theleft-handwinding of relay 4C3 battery and ground. This signal to the callingsubscriber will indicate that all the trunks to the private branchexchange are busy,-and the subscriber may at his option either hang upand release the connection or remain ,at histelephone in which case hewill be switched to the private branch exchange system as soon as one ofthe trunks become idle. As soon as one. of the trunks of the privatebranch exchange is disengaged and they finder associated with thistrunlcrestoredto normal, the circuit of its motor magnet 19will beclosed by virtue of the attracted armature of the relayz 17 associatedwith the trunkselected' by the connector switch and the. finder will beimmediately. operated to hunt for the terminals of the trunk selected.As soon as this trunk has been found, a signal will be displayed .at theprivate branch exchange due to the battery bridged across the linestrands of the trunk by the-,battery feed relay 43. The callingsubscriber may now be onnected 120 to the desired private branchexchange subscriber.

Obviously the invention is not limited to the specific. embodimentherein, shown and described, but is capable of many variations 125 andmodifications without departing from its spirit and scope.

What is claimed is:

1. In an automatic telephone. system, the combination with a pluralityof subscrib- 180 ers lines, of private branch exchange trunk lines,means including a connector switch for establishing connection betweensaid subscribers lines and said trunk lines,means to indicate to thecalling subscriber when all of said private branch exchange trunk linesare busy, and means to automatically connect the first idle trunk to theprivate branch exchange with the calling line.

2. In an automatic telephone system, the combination with a plurality ofsubscribers lines, of private branch exchange trunk lines, meansincluding a connector switch for establishing connection between saidsubscribers lines and said trunk lines, stationary terminals in eachconnector switch assigned to said private branch exchange trunk lines,other trunk lines, a finder switch associated with each one of saidprivate branch exchange trunk lines and with all of said other trunklines, means to indicate to the calling subscriber when all of said private branch exchange trunk lines are busy, and means to start the finderswitch associated with the first idle trunk to automatically connectsaid trunk with said calling line.

3. In a telephone system, the combination with a plurality ofsubscribers lines, a private branch exchange system, of a plurality oftrunks to said private branch exchange system, means including aconnector switch for interconnecting said subscribers lines, terminalsin said connector switch assigned to the trunks of said private branchexchange system, means when a calling subscriber selects the terminalsin a connector switch assigned to a private branch exchange system toindicate to the calling subscriber that all the private branch exchan etrunks are busy, switches allotted to said private branch exchangetrunks, and means actuated when one of said trunks becomes idle toconnect the calling subscriber with said idle trunk line.

4. In an automatic telephone system, the combination with a'plurality ofsubscribers lines, of a group of trunk lines, means for establishing aconnection between said subscribers lines and said trunk lines, means toindicate to the calling subscriber when all of said trunk lines arebusy, and means automatically to connect the first idle trunk to thecalling line.

5. In an automatic telephone system, the combination with telephonelines, of a group of trunk lines, automatic switches for connecting anyof said telephone lines with any of said trunk lines, meansautomatically actuated by the busy condition of all the trunks of agroup for transmitting a busy signal to the calling party and meansautomatically actuated when one of said trunks becomes idle, for causingone of said automatic switches to extend the calling line to said trunk.

6. In an automatic telephone system, the

combination with telephone lines, of a group of trunk lines, automaticswitches for connecting any of said telephone lines with any of saidtrunk lines, means automatically actuated by the busy condition of allthe trunks of a group for transmitting busy signals to calling partiesand means automatically actuated as said trunks become idle forsuccessively setting said automaticswitches in operation to extend thecalling lines.

In witness whereof, I hereunto subscribe my name this 22nd day of April,A. D.,

JACOB IV. LATTIG. In witness whereof, I hereunto subscribe my name this7th day of April, A. D., 1916.

CHARLES L. GOODRUM.

Copies 0! this patent may be obtained for flye cents each, by addressingthe Commissioner of Patents, Washington, D. 0.

